Non-contact voltage sensing method and apparatus

ABSTRACT

A non-contact electric potential meter system to determine voltage between an AC conductor and a reference potential without direct electrical contact to the conductor. A housing provides a shielded measurement region that excludes other conductors and holds power supply means; an AC voltage sensing mechanism includes a conductive sense plate and an electrical connection to the reference potential. Waveform-sensing electronic circuitry obtains an AC voltage waveform induced by capacitive coupling between the conductor and the conductive sense plate. Capacitance-determining electronic circuitry obtains a scaling factor based on the coupling capacitance formed between the conductor and the conductive sense plate. Signal processing electronic circuitry uses the AC voltage waveform and the coupling capacitance-based scaling factor to obtain the voltage between the conductor and the reference potential.

FIELD

This disclosure is directed to improved systems and methods of measuringelectric potential in an alternating current (“AC”) conductor.

BACKGROUND

Traditional approaches to measure AC voltage require making electricalcontact with a target conductor and with a reference potential, forminga path with a voltmeter in parallel with the circuit to be measured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating operational components of anexample non-contact voltage sensing apparatus in accordance with variousembodiments.

FIG. 2 illustrates an exploded isometric view of components of anexample non-contact voltage sensing apparatus in accordance with oneembodiment.

FIG. 3 illustrates a different exploded breakout view of components ofan example non-contact voltage sensing apparatus in accordance with oneembodiment.

FIG. 4 illustrates a perspective view of an assembled examplenon-contact voltage sensing apparatus in accordance with one embodiment.

FIG. 5 illustrates an operational routine of a non-contact voltagesensing system in accordance with one embodiment.

FIG. 6 is a wiring diagram schematically illustrating a multiplexingcircuit of electrical components configured to measure a waveform and acapacitance in accordance with one embodiment.

FIG. 7 is a wiring diagram schematically illustrating electricalcomponents of a waveform detector circuit in accordance with oneembodiment.

FIG. 8 is a wiring diagram schematically illustrating electricalcomponents of a capacitance detector circuit in accordance with oneembodiment.

FIG. 9 is a wiring diagram schematically illustrating electricalcomponents of a calibration circuit configured to calibrate acapacitance detector circuit in accordance with one embodiment.

FIGS. 10A-10B are graphs illustrating a sensitivity of sensedcapacitance to conductor size and distance from a conductive senseplate.

FIG. 11 illustrates physical components of an example conductor fixingand measurement system including a digital caliper in accordance withone embodiment.

FIG. 12 is a wiring diagram schematically illustrating multiphasecoupling capacitances.

DETAILED DESCRIPTION

This application discloses a non-contact electric potential meter systemsuitable for obtaining a determination of a voltage between a referencepotential and an energized or “hot” conductor of an alternating currentelectrical circuit, without direct electrical contact to the first hotconductor and without reference to any other AC voltage signal.

The technical advancements of the non-contact voltage sensing apparatusdisclosed herein allow it to overcome the limitations of prior powermeters and offer significant advantages over prior art electric voltagemeasuring devices. For example, the disclosed voltage sensing apparatususes a non-contact capacitive coupling system and technique to measurethe voltage signal in an AC conductor. This allows accurate voltagesensing—measurement of a properly shaped and scaled waveform, not justpeak detection—without requiring physical contact to the hot conductorwire.

The disclosed technology obtains an AC waveform in a target energizedconductor via capacitive coupling between the conductor and a senseplate that is situated near the conductor. An electronic circuit samplesa waveform representing a filtered version of the AC voltage between theenergized conductor and a reference potential. Another circuitdetermines the coupling capacitance between the conductor and the senseplate. Together, these allow analog or digital signal processingcircuitry to recover the shape or frequency spectrum of the line voltageand to correctly scale the recovered waveform. Thus, the non-contactvoltage sensing apparatus disclosed herein accurately determines the ACline voltage.

In addition, the disclosed technology allows a split-core currenttransformer (CT) to provide current measurements of the targetconductor, and provides a multiplexing circuit to repurpose the currenttransformer (when it is not actively measuring current) as an energyharvester to supply runtime power for the non-contact voltage sensingapparatus. In some embodiments, a CT functions as a current sensor andenergy harvester without multiplexing. For example, by estimation orcalculation of energy harvester output voltage, current, or power, bothenergy harvesting and current sensing functions may be operated at thesame time. Harvesting energy to power the non-contact voltage sensingapparatus and simultaneously measuring the current flowing in the targetconductor can increase energy efficiency. For another example,components (such as energy harvesting electronic circuitry) may beturned off when current sensing circuitry is active.

Reference is now made in detail to the description of the embodiments asillustrated in the drawings. While embodiments are described inconnection with the drawings and related descriptions, there is nointent to limit the scope to the embodiments disclosed herein. On thecontrary, the intent is to cover all alternatives, modifications, andequivalents. In alternate embodiments, additional sensing devices, orcombinations of illustrated devices, may be added to, or combined,without limiting the scope to the embodiments disclosed herein. Each ofthe Figures discussed below may include many more or fewer componentsthan those shown and described. Moreover, not all of the describedcomponents may be required to practice various embodiments, andvariations in the arrangements and types of the components may be made.However, the components shown are sufficient to disclose variousillustrative embodiments for practicing the disclosed technology.

The embodiments set forth below are primarily described in the contextof measuring electric circuits such as residential, commercial,industrial, or utility-level wiring (including, e.g., power transmissionand distribution networks). However, the embodiments described hereinare illustrative examples and in no way limit the disclosed technologyto any particular size, construction, or application of conductor.

The phrases “in one embodiment,” “in various embodiments,” “in someembodiments,” and the like are used repeatedly. Such phrases do notnecessarily refer to the same embodiment. The terms “comprising,”“having,” and “including” are synonymous, unless the context dictatesotherwise. As used in this specification and the appended claims, thesingular forms “a,” “an,” and “the” include plural referents unless thecontent clearly dictates otherwise. For example, “a scaling factor”generally includes multiple scaling factors. It should also be notedthat the term “or” is generally employed in its sense including “and/or”unless the content clearly dictates otherwise.

The terms “sense”/“sensing,” “meter”/“metering,” “detect”/“detecting,”and “measure”/“measuring” are generally synonymous, unless the contextdictates otherwise. For example, “detecting” an AC waveform generallyrefers to obtaining measurement of a continuously varying alternatingcurrent, and not only obtaining a Boolean value representing whether anAC waveform is present. A “detector” likewise should be interpreted as adevice to obtain measurements and not only to detect presence. The terms“electric” and “electrical” are generally synonymous. The terms“voltage” and “potential” or “electric(al) potential” are also generallysynonymous. Similarly, the terms “amperage” and “current” or“electric(al) current” are generally synonymous. Thus, the terms“voltage sensing apparatus” and “electric potential meter system” areused synonymously.

The disclosed non-contact voltage sensing apparatus can take a varietyof form factors. FIGS. 1 through 12 illustrate a variety of differentarrangements, designs, and subsystem possibilities. The illustratedsensing systems and methods are not an exhaustive list; in otherembodiments, a measurement region for receiving a conductor or circuitryfor powering and/or controlling a non-contact voltage sensing apparatuscould be formed in different arrangements. However, it is not necessaryto exhaustively show such optional implementation details to describeillustrative embodiments.

FIG. 1 is a block diagram illustrating operational components of anexample non-contact voltage sensing apparatus 100 in accordance with oneembodiment. The apparatus 100 typically includes a housing 110. Theapparatus 100 includes a measurement region 120 that is configured toreceive a conductor, e.g., a “hot” AC conductor (or “line”) such as aninsulated copper wire. The non-contact voltage sensing apparatus 100 isconfigured so that when the measurement region 120 receives theconductor, the conductor is not interrupted. In various embodiments, themeasurement region 120 in operation receives a single conductor, and isconfigured to exclude other conductors (including, e.g., any additional“hot” wire). In various embodiments, the housing 110 provides, defines,or indicates the measurement region 120. In various embodiments, themeasurement region 120 is configured such that the conductor passesalong, into, or through the measurement region 120. Thus, themeasurement region 120 may be arranged inside and/or outside the housing110.

The non-contact voltage sensing apparatus 100 further includes a shield125. The shield 125 may be constructed of material having highconductivity, such as a metallic foil or mesh. In various embodiments,the shield 125 may form a Faraday cage around a portion or all of thecomponents of the non-contact voltage sensing apparatus 100, such asaround the measurement circuitry and conductive sense plate describedbelow with respect to this FIG. 1. In some embodiments, the shield 125may extend only partly around a portion or all of the components of thenon-contact voltage sensing apparatus 100, and/or may include one ormore apertures, e.g., to accommodate a conductor in the measurementregion 120. In some embodiments, the shield 125 does not surround themeasurement region 120. In some embodiments, the shield 125 is connectedto a ground potential.

The illustrated non-contact voltage sensing apparatus 100 includes acapacitive AC voltage sensing mechanism 140. The voltage sensingmechanism 140 includes components configured to obtain a determinationof an AC voltage in a conductor in the measurement region 120, such asby sensing an AC line voltage waveform, determining a scaling factorbased on coupling capacitance, and processing the waveform and thescaling factor as further described in this disclosure.

The capacitive AC voltage sensing mechanism 140 includes a conductivesense plate 130 configured so that the conductive sense plate 130 formsa capacitive coupling with a conductor in the measurement region 120.The non-contact voltage sensing apparatus 100 further includes anelectrical connection to a reference potential 145, used in determininga voltage between the conductor and the reference potential. Theelectrical connection to a reference potential 145 may include aresistive or capacitive connection to a ground potential.

In various embodiments, the non-contact voltage sensing apparatus 100 isconfigured so that the conductive sense plate 130 has a determined orotherwise determinable geometric relationship to the conductor when themeasurement region 120 receives the conductor. The geometricrelationship between the conductor and the conductive sense plate 130,and, e.g., the size or other physical characteristics of the conductor(such as a wire gauge and/or insulation jacket thickness) may be known,fixed, or pre-set; or they may be measurable or similarly determinable.In some embodiments, the non-contact voltage sensing apparatus 100includes conductor measurement means 131 to fix and/or measure one ormore aspects of the conductor at the measurement region 120. An exampleconductor measurement means 131 and digital caliper electronic circuitry133 is described in further detail with reference to FIG. 11 below. Insome embodiments, the non-contact voltage sensing apparatus 100 includesa humidity sensor 135, so that the apparatus 100 can identify andcompensate for changes in the dielectric constant of air associated withchanges in humidity.

The capacitive AC voltage sensing mechanism 140 includeswaveform-sensing electronic circuitry 142 configured to sense an AC linevoltage waveform. The waveform-sensing electronic circuitry 142 mayobtain the AC waveform by measuring a current induced via capacitivecoupling between the sense plate 130 and an energized conductor in themeasurement region 120. The waveform-sensing electronic circuitry 142may include an operational amplifier (“op-amp”) circuit, such asdescribed in further detail with reference to FIG. 7 below.

The capacitive AC voltage sensing mechanism 140 further includescapacitance-determining electronic circuitry 144 (also referred toherein as coupling capacitance tracking electronic circuitry) configuredto sense a coupling capacitance between the conductive sense plate 130and the conductor in the measurement region 120. In some embodiments,the capacitance-determining electronic circuitry 144 includes elementshaving an output frequency that depends in part on the couplingcapacitance, such as described in further detail with reference to FIG.8 below.

The capacitive AC voltage sensing mechanism 140 further includes signalprocessing electronic circuitry 146. The signal processing electroniccircuitry 146 processes the AC line voltage waveform representationobtained by the waveform-sensing electronic circuitry 142 to recover ashape or frequency spectrum of the line voltage waveform. The signalprocessing electronic circuitry 146 may process the coupling capacitancedetermination obtained by the capacitance-determining electroniccircuitry 144 to obtain a scaling factor. The signal processingelectronic circuitry 146 may also use the determination of one or morephysical characteristics of the conductor obtained by the conductormeasurement means 131 (e.g., via the digital caliper electroniccircuitry 133) to obtain a scaling factor. The signal processingelectronic circuitry 146 scales the recovered shape or frequencyspectrum of the line voltage waveform according to the scaling factor(s)to obtain an accurate measurement of the true AC line voltage in theconductor in the measurement region 120. In various embodiments, thesignal processing electronic circuitry 146 may include analog and/ordigital signal processing components.

In some embodiments, the non-contact voltage sensing apparatus 100includes a current sensing mechanism 150. The current sensing mechanism150 may include a current transformer (“CT”) 151, a current sensor 152,and current processing electronic circuitry 155. The current sensor 152may be a split-core current transformer, a solid-core currenttransformer, a Rogowski coil, an anisotropic magnetoresistance (AMR)sensor, a giant magnetoresistance (GMR) sensor, a Hall effect sensor, acurrent-sensing resistor, an inductor, etc. In some embodiments, thesignal processing electronic circuitry 146 can process andtime-synchronize a current waveform and a voltage waveform to obtain adetermination of a power factor based on the detected AC electriccurrent and voltage.

In various embodiments, the non-contact voltage sensing apparatus 100includes power supply means 160 configured to power the electroniccircuitry of the non-contact voltage sensing apparatus 100. For example,the power supply means 160 may include a stored energy system such as acapacitor or battery 164; an external power supply such as a directcurrent (“DC”) voltage source 166; or means for obtaining energy from anAC conductor, such as energy harvesting electronic circuitry 162. Forexample, the power supply means 160 may be configured to obtain powerfrom the conductor via the measurement region 120, e.g., via the currenttransformer 151 of the current sensing mechanism 150.

In various embodiments, the non-contact voltage sensing apparatus 100includes control circuitry 180. The control circuitry 180 may includemultiplexing circuitry 185 configured to share or switch componentsamong or between circuits. For example, the control circuitry 180 maymultiplex 185 the conductive sense plate 130 between thewaveform-sensing electronic circuitry 142 and thecapacitance-determining electronic circuitry 144. As another example,the control circuitry 180 may multiplex 185 the current transformer 151between the current sensing mechanism 150 and the energy harvestingelectronic circuitry 162. The multiplexing circuitry 185 may reconfiguresubcircuits to include or exclude components such that they can performmultiple functions without interfering with one another. Themultiplexing circuitry 185 may operate according to various algorithmsbased on time (e.g., at even, uneven, or irregular intervals oraccording to a schedule), need (e.g., based on one or more signalsreceived by the control circuitry 180, such as a battery 164 level),sensed voltage and/or current values, or other factors.

In addition, the control circuitry 180 may be configured to combineproperly scaled sampled waveforms measured by the voltage sensingmechanism 140 (e.g., by the waveform-sensing electronic circuitry 142,scaled according to the capacitance-determining electronic circuitry144) with current measurements obtained by the current sensing mechanism150, allowing the non-contact voltage sensing apparatus 100 to calculatea power dissipation, power delivery, or power factor, among otherpossible calculations including real, reactive, and apparent power.

In various embodiments, a data bus connects the various internal systemsand logical components of the non-contact voltage sensing apparatus 100.For example, the control circuitry 180 may include circuitry to causemeasurements to be recorded to memory 190 and/or transmitted viainput/output (“I/O”) components 170 such as a radio 175 transceiver fortransmitting and/or receiving radio frequency (“RF”) signals (e.g., vialow-power wide-area network (“LPWAN”) [e.g., LoRa, Sigfox, LTE-M,NB-IoT, etc.], Bluetooth, Wi-Fi, ZigBee, cellular network connection,NFC, RFID, etc.) or other interface (e.g., a wired communication portsuch as USB, UART, etc.). The I/O components 170 may allow data(including, e.g., recorded voltage measurements) to be sent from thenon-contact voltage sensing apparatus 100 to an external device ordestination. The I/O components 170 may also allow instructions to betransmitted to the control circuitry 180 or other components of thenon-contact voltage sensing apparatus 100 such as the memory 190. TheI/O components 170 may interface with, e.g., specialized meter readingdevices, mobile phones, desktop computers, laptops, tablets, wearablecomputers, or other computing devices that are configured to connect tothe non-contact voltage sensing apparatus 100.

The memory 190 can include a combination of temporary and/or permanentstorage, and both read-only memory (“ROM”) and writable memory (e.g.,random access memory (“RAM”), processor registers, and on-chip cachememories), writable non-volatile memory such as flash memory or othersolid-state memory, hard drives, removable media, magnetically oroptically readable discs and/or tapes, nanotechnology memory, syntheticbiological memory, and so forth. A memory is not a propagating signaldivorced from underlying hardware; thus, a memory and acomputer-readable storage medium do not refer to a transitorypropagating signal per se. The memory 190 includes data storage thatcontains programs, software, and/or information, such as an operatingsystem (e.g., an embedded real-time operating system), applicationprograms or functional routines, and data (e.g., data structures,database entries, waveform representations, measurement records,calculation results, etc.).

The non-contact voltage sensing apparatus 100 may include a subset orsuperset of the components described above. Additional components mayinclude, e.g., a display screen (such as an LCD, LED, or OLED displayscreen or an e-ink display), a speaker for playing audio signals, ahaptic feedback device for tactile output such as vibration, etc., anenvironmental sensor such as a temperature sensor, power managing orregulating systems, etc. In various embodiments, additionalinfrastructure as well as additional devices may be present. Further, insome embodiments, the functions described as being provided by some orall of the non-contact voltage sensing apparatus 100 may be implementedvia various combinations of physical and/or logical devices, e.g., oneor more replicated and/or distributed physical or logical devices. Forexample, in some embodiments, the non-contact voltage sensing apparatus100 includes a sensor configured to capture and wirelessly transmitvoltage parameters (shape, frequency components and phases, etc.) to anexternal device, and may or may not include any current sensing orsignal processing circuitry.

Aspects of the non-contact voltage sensing apparatus 100 can be embodiedin a specialized or special purpose computing device or data processorthat is specifically programmed, configured, or constructed to performone or more of the computer-executable instructions explained in detailherein. For example, the control circuitry 180 can be embodied in amicrocontroller or an application-specific integrated circuit (“ASIC”).Various circuits or circuitry of the non-contact voltage sensingapparatus 100 may include or be embodied in a processing component thatcontrols operation of the non-contact voltage sensing apparatus 100 inaccordance with computer-readable instructions stored in memory 190. Aprocessing component may be any logic processing unit, such as one ormore central processing units (“CPUs”), graphics processing units(“GPUs”), digital signal processors (“DSPs”), field-programmable gatearrays (“FPGAs”), ASICs, etc. A processing component may be a singleprocessing unit or multiple processing units in an electronic device ordistributed across multiple devices. Aspects of the disclosed systemsand methods can also be practiced in distributed computing environmentswhere tasks or modules are performed by remote processing devices thatare linked through a communications network, such as a local areanetwork (LAN), wide area network (WAN), or the Internet, e.g., computingresources provisioned from a “cloud computing” provider. In adistributed computing environment, modules can be located in both localand remote memory storage devices. For example, in some embodiments, thenon-contact voltage sensing apparatus 100 includes a sensor configuredto capture voltage parameters at a first location, and signal processingcircuitry at a second location remote from the first location. Suchimplementations allow remote voltage sensing around an electricalnetwork at low cost with centralized computational resources.

Alternative implementations of the systems disclosed herein can employsystems having blocks arranged in different ways; and some blocks can bedeleted, moved, added, subdivided, combined, and/or modified to providealternative or sub combinations. Each of these blocks can be implementedin a variety of different ways. However, it is not necessary to showsuch infrastructure and implementation details or variations in FIG. 1in order to describe an illustrative embodiment.

FIG. 2 illustrates an exploded isometric view of components of anexample non-contact voltage sensing apparatus 200 in accordance with oneembodiment. The example non-contact voltage sensing apparatus 200includes a housing in two parts: an upper housing 210 and a lowerhousing 215. The upper housing 210 includes an upper hinge part 214, andthe lower housing 215 includes a lower hinge part 216. Together, theupper hinge part 214 and the lower hinge part 216 form a hinge thatallows the upper housing 210 and the lower housing 215 to hinge open andremain connected, providing an advantageous way to place the non-contactvoltage sensing apparatus 200 around a conductor. When the hinges 214,216 are engaged and the upper housing 210 and lower housing 215 areclosed, a hook 212 on the upper housing 210 engages with a bar 218 onthe lower housing 215 to secure the non-contact voltage sensingapparatus 200 around a conductor. The illustrated hinge and closuremechanisms are examples; alternative approaches could include any of awide variety of mechanisms such as a friction fit or snap fit betweenthe upper housing 210 and lower housing 215, a screw-on attachment, amagnetic attachment, a locking pin, a fastener securement, ahook-and-loop fabric securement, another style of mechanical latch, etc.Implementations without a split-core current transformer (e.g., with aone-piece transformer core or no current transformer) may have a housingin one part and include no closure mechanism at all.

When the non-contact voltage sensing apparatus 200 is closed, itprovides a measurement region 220 for a conductor. In the illustratedembodiment, the measurement region 220 passes through the non-contactvoltage sensing apparatus 200. In other embodiments, the measurementregion may be arranged in other ways, such as along a non-contactvoltage sensing apparatus, so that the apparatus can measure voltage ina conductor located at or against the apparatus without requiring theconductor to pass through the apparatus.

Adjacent to the measurement region 220 is a conductive sense plate 230.The conductive sense plate 230 is electrically connected to circuitry orelectronics 240 by a connection 235.

The non-contact voltage sensing apparatus 200 includes a currenttransformer (e.g., a ferro-magnetic core, such as a ferrite ornanocrystalline core) divided into two parts: an upper core 251 withinthe upper housing 210, and a lower core 252 within the lower housing215. The upper core 251 and the lower core 252 come together to form acomplete loop around the measurement region 220. In some embodiments,the current transformer (CT) is one piece rather than a split core,which may only partially surround a conductor or may require a conductorto be threaded through the current transformer core. When a conductor isenergized in the measurement region 220 and the non-contact voltagesensing apparatus 200 is closed around the conductor, windings 253around the lower core 252 and connected to the electronics 240 enablethe current transformer to sense current through the conductor and/orharvest energy from the conductor.

The present disclosure encompasses various arrangements and shapes ofvoltage sensing systems, and is not limited to the embodiment describedvia this illustrative example.

FIG. 3 illustrates a different exploded breakout view of components ofan example non-contact voltage sensing apparatus 300 in accordance withone embodiment. This illustration of an example non-contact voltagesensing apparatus 300 includes elements of the non-contact voltagesensing apparatus 200 of FIG. 2. For example, it includes the componentsof the housing: the upper housing 210 and the lower housing 215, theupper hinge part 214 and the lower hinge part 216, the hook 212 on theupper housing 210 that engages with the bar 218 on the lower housing215. The example non-contact voltage sensing apparatus 300 also includesthe measurement region 220, around which are situated the upper core 251and the lower core 252 that form the core of the current transformer(the windings 253 are not shown in this illustration).

In this embodiment, resilient foam pieces 310 are configured to fitwithin the upper housing 210, on opposite sides of the currenttransformer upper core 251. The resilient foam pieces 310 provide amechanical spring force to press a conductor in the measurement region220 toward the conductive sense plate 230 when the non-contact voltagesensing apparatus 300 is assembled and closed around a conductor. Invarious embodiments, other mechanical means may be employed to fix orlocate a conductor within the non-contact voltage sensing apparatus 300,e.g., a spring or a spring-loaded plate to provide a pushing force on aconductor, or a strap or clip to pull a conductor into a position.

The lower core 252 and an aligner 350 are shown, for illustrativepurposes, out of the order in which they would be assembled in thisexample non-contact voltage sensing apparatus 300. In operation, thealigner 350 and lower core 252 would be located below the carrier 330for the conductive sense plate 230. Similarly, for visibility theelectronics 240 are shown broken out outside the lower housing 215.

In this embodiment, a separator 320 separates the measurement region 220from the conductive sense plate 230, and in operation below it thecarrier 330, the aligner 350, the current transformer lower core 252,and the electronics 240. The separator 320 is illustrated as a plasticpiece having a thickness of approximately 1 mm In various embodiments,the separator 320 can be formed of various materials, be of variousthicknesses, be of implicit construction (so that a space is providedbetween the measurement region 220 and the conductive sense plate 230)or be omitted (so that no space is provided between the measurementregion 220 and the conductive sense plate 230).

In the illustrated embodiment, the conductive sense plate 230 is aconductive metal layer on a flexible printed circuit board (“PCB”) withan insulating layer, e.g. polyamide. The connection 235 is made of thesame material. The conductive sense plate 230 is shown configured with acurve or the flexibility to curve around a conductor in the measurementregion 220 to improve capacitive coupling, e.g., by providing a reducedaverage distance between the conductive sense plate 230 and theconductor. A conductive sense plate 230 may also be flat (e.g., forsimplicity of manufacture) or have a different shape.

In this example embodiment, the electronics 240 include three PCBs 342,344, 346. In an implementation, each PCB may include circuitry toperform a discrete function or set of functions. For example, theelectronics 240 may include a voltage sensing circuitry PCB 342, anenergy harvesting and current sensing circuitry PCB 344, and amicrocontroller and RF communication circuitry PCB 346. Anotherembodiment could integrate some or all of these functions onto a singlePCB. Yet another embodiment could integrate some or all of thesefunctions into an ASIC.

FIG. 4 illustrates a perspective view of an assembled examplenon-contact voltage sensing apparatus 400 in accordance with oneembodiment. The upper housing 210 and the lower housing 215 of FIG. 2are closed, and the hook 212 on the upper housing 210 is engaged withthe bar 218 on the lower housing 215. This illustrates an elegantclosure by which a person can simply press on the hook 212 to release itfrom the bar 218 and open the non-contact voltage sensing apparatus 400(via the hinge, which is not visible) for placing the apparatus 400onto, or removing it from, a conductor 420. The example non-contactvoltage sensing apparatus 400 shows, by dashed line, a conductor 420located in the measurement region of the apparatus 400, pressed into aposition relative to the conductive sense plate by the mechanical springforce from the resilient foam pieces 310.

FIG. 5 illustrates an operational routine 500 of a non-contact voltagesensing system in accordance with one embodiment. In variousembodiments, the operational routine 500 is performed by one or morenon-contact voltage sensing apparatuses such as those illustrated abovewith reference to FIGS. 1-4. Portions of the operational routine 500 maybe performed by circuitry such as illustrated below with reference toFIGS. 6-9. As those having ordinary skill in the art will recognize, notall events of an operational routine are illustrated in FIG. 5. Rather,for clarity, only those aspects reasonably relevant to describing thenon-contact sensing of an AC voltage are shown and described. Thosehaving ordinary skill in the art will also recognize that the presentedembodiment is merely one example embodiment and that variations on thepresented embodiment may be made without departing from the scope of thebroader inventive concept set forth in the description herein and theclaims below. The operational routine 500 begins in starting block 501.

In block 515, the operational routine 500 receives a single AC conductorin or at a measurement region. As described above with reference toFIGS. 1 and 2, a measurement region for a conductor may be arranged sothat the conductor passes along, into, or through the measurement regionprovided by the housing. The operational routine 500 receives a singleAC conductor and excludes other conductors.

In block 525, the operational routine 500 shields some or all of themeasurement region and/or the measurement circuitry or electronics. Thisallows the operational routine 500 to reduce interference from otherconductors that may be nearby, and thus to improve the quality (e.g.,precision and accuracy) of voltage measurement relative to a referencepotential. For example, in a multiphase (e.g., three-phase) electricalsystem, conductors of alternate phases may produce unwanted capacitancesto a conductive sense plate, as described below with reference to FIG.12. In such an environment, arranging shielding to help isolatecapacitance to the target conductor can enable the operational routine500 to provide improved results.

In block 535, the operational routine 500 obtains an AC waveform bymeasuring a current induced via capacitive coupling between theenergized conductor in the measurement region and a conductive senseplate of the non-contact voltage sensing apparatus. Examplewaveform-sensing electronic circuitry is described in further detailwith reference to FIG. 7 below. The operational routine 500 may samplean AC waveform, though the sampled waveform may be a filtered and/ordistorted representation of a voltage between the energized conductorand a reference potential.

The illustrated operational routine 500 branches to show two alternativeapproaches to determine a coupling capacitance and/or a scaling factorbased on coupling capacitance. One branch includes blocks 540, 550, and560; the other branch includes blocks 545 and 555. Variousimplementations of a non-contact voltage sensing system may utilizeeither approach, or combinations or permutations thereof.

Turning to the approach illustrated in blocks 540, 550, and 560: in someimplementations, the routine 500 uses capacitance-determining electroniccircuitry to measure a coupling capacitance between the energizedconductor in the measurement region and the conductive sense plate ofthe non-contact voltage sensing apparatus. In block 540, the routine 500calibrates the capacitance-determining electronic circuitry. Calibrationmay be performed under controlled conditions at the time of manufacture.Calibration may also be performed during operation, e.g., to correct foreffects of parasitic capacitance. Example calibration circuitry isdescribed in further detail with reference to FIG. 9 below.

In block 550, the operational routine 500 senses the couplingcapacitance between the energized conductor and the conductive senseplate. For example, the routine 500 may determine the couplingcapacitance using the capacitance-determining electronic circuitrycalibrated in block 540. In some embodiments, the operational routine500 produces a value for the coupling capacitance; in other embodiments,the operational routine 500 obtains an indication that does not directlyprovide a value for the coupling capacitance but may be used to producea scaling factor for signal processing.

In block 560, the operational routine 500 determines a scaling factorbased at least in part on the coupling capacitance between the conductorand the conductive sense plate of the non-contact voltage sensingapparatus. Example scaling factor- or capacitance-determining electroniccircuitry is described in further detail with reference to FIG. 8 below.

Turning to the approach of blocks 545 and 555: in some implementations,the routine 500 measures a dimension of a conductive wire located in orat the measurement region. In block 545, the operational routine 500fixes (or determines) the location of the conductor received in block515 and determines a size of the conductor. To facilitate both physicalmeasurement of the conductor and consistent electric measurement ofvoltage in the conductor, the routine 500 provides a mechanism forholding the conductor in a place or position. Some example mechanismsare described above with reference to FIG. 3 and below with reference toFIG. 11.

For example, a digital caliper may determine a width or diameter of aconductor including its insulating jacket. In other embodiments, anoptical measuring system may determine a size of the conductor. In otherembodiments, a measurement device may, e.g., obtain a circumferentialmeasurement of a conductor, or use a shaped aperture (e.g., a vee shapeor stepped opening) to locate a conductor according to its size. In someembodiments, the routine 500 determines a wire gauge or cross-sectionalarea of the conductor based on a measurement of the conductor. Forexample, the routine 500 may determine that a range of diameters of anyconductive wire plus its insulating jacket corresponds to a particulargauge of wire. Thus, even though different brands of conductors may havedifferent thicknesses of insulation and therefore overall diameters, theoperational routine 500 can accurately determine a size of theconductive wire to provide an improved contactless determination of avoltage in the conductor.

In block 555, the operational routine 500 determines a scaling factor orcoupling capacitance between the conductor and the conductive senseplate of the non-contact voltage sensing apparatus. In this approach,capacitance-determining electronic circuitry is configured to produce ascaling factor or estimated capacitance from a combination of fixed orknown factors (e.g., the size of the conductive sense plate and distancefrom the conductive sense plate to the measurement region) and measuredvariables (e.g., the location and/or size of the target hot conductor).The operational routine 500 may determine the scaling factor or couplingcapacitance based in part on the determination of the size of theconductor from block 545, so that the routine 500 accounts for how agauge of the conductive wire affects the coupling capacitance.

For example, based on the geometry of the measurement space and locationof the conductor relative to the conductive sense plate, together withthe size of the conductor determined in block 545, the routine 500 canperform a calculation or use a lookup table to obtain a computedcapacitance or scaling factor.

In block 565, the operational routine 500 performs signal processingwith respect to the AC waveform obtained in block 535 and the scalingfactor or coupling capacitance determined in block 560 or block 555. Asdescribed above with reference to FIG. 1, the routine 500 processes theobtained waveform representation and may recover a shape or frequencyspectrum of the line voltage waveform. The operational routine 500processes the coupling capacitance and/or the size of the conductor andmay obtain a scaling factor. This may include multiple scaling factors,e.g., scaling factors that are frequency dependent and/or scalingfactors that account for different influences on the obtained waveformrepresentation. The operational routine 500 performs signal processingthat scales the obtained waveform representation (e.g., the recoveredshape or frequency spectrum of the line voltage waveform) based on thecoupling capacitance (e.g., according to the scaling factor(s)).

In some implementations, the routine 500 applies one or more scalingfactors to account for, e.g., nonlinearities in a circuit, attenuationat particular frequencies, or complex impedances, to separate outmultiple correction factors that may affect measurement. In someimplementations, calibration of a circuit may provide an additionalscaling factor to account for parasitic capacitance.

In block 575, the operational routine 500 determines, based on thesignal processing in block 565, an AC voltage of the conductor relativeto a reference potential. The operational routine 500 is thus able todetermine conductor voltage without interrupting the conductor, withoutcontact to the conductor wire, and without reference to any other ACsignal.

The operational routine 500 ends in ending block 599.

Alternative implementations of the operational routine 500 can performroutines having processes in a different order, and some processes orblocks can be deleted, moved, added, subdivided, combined, and/ormodified to provide alternative or sub combinations. Each of theseprocesses or blocks can be implemented in a variety of different ways.While some processes or blocks may be shown as being performed inseries, they may instead be performed or implemented in parallel, or canbe performed at different times.

FIG. 6 is a wiring diagram schematically illustrating a multiplexingcircuit 600 of electrical components configured to measure a waveformand a capacitance in accordance with one embodiment. A hot conductor 620carries an AC line current and voltage to be measured by a non-contactvoltage sensing apparatus. The line voltage 625 in conductor 620 islabeled “V_(line)” in FIGS. 6-9. The hot conductor 620 is part of anelectrical circuit that typically includes a load (not shown), a neutral615 (e.g., a line, conductor, bus, or node), and a connection to earth610.

The hot conductor 620 is capacitively coupled with a conductive senseplate 630. The capacitance 635 between the conductive sense plate 630and the hot conductor 620 is labeled “C_(sense)” in FIGS. 6-9 and 12. Invarious embodiments, the conductive sense plate 630 may comprise one ormore components of a capacitor such as the conductive sense plate 130described above with reference to FIG. 1 or the conductive sense plate230 described above with reference to FIGS. 2-3.

The conductive sense plate 630 may be switchably connectable to awaveform detector 650 (e.g., waveform-sensing electronic circuitry suchas described in further detail with reference to FIG. 7 below) viaswitch S₀ 640, and/or to a capacitance detector 660 (e.g.,capacitance-determining electronic circuitry such as described infurther detail with reference to FIG. 8 below) via switch S₁ 645. Insome embodiments, switches S₀ 640 and S₁ 645 are physically connected orlogically controlled so that when switch S₀ 640 is closed, switch S₁ 645is open, and/or vice versa. For example, switch S₀ 640 and switch S₁ 645can be implemented as one single-pole double-throw (“SPDT”) switch. Insuch embodiments, the conductive sense plate 630 is switched between thewaveform detector 650 and the capacitance detector 660 so that theconductive sense plate 630 is connected to either the waveform detector650 or the capacitance detector 660 but not to both at the same time.

In some embodiments, switches S₀ 640 and S₁ 645 can be switchedindependently, e.g., allowing both to be in an open state so that theconductive sense plate 630 is connected to neither the waveform detector650 nor the capacitance detector 660. In some embodiments, switches S₀640 and S₁ 645 can be switched such that both are in a closed state sothat the conductive sense plate 630 is connected to both the waveformdetector 650 and the capacitance detector 660 at the same time. In someembodiments, the switches S₀ 640 and S₁ 645 are connected to separateconductive sense plates 630, such that the waveform detector 650 isswitchably connected to one conductive sense plate 630 and thecapacitance detector 660 is switchably connected to another conductivesense plate 630.

In an embodiment in which the conductive sense plate 630 is configuredto be switchable between the waveform detector 650 and the capacitancedetector 660, the switches S₀ 640 and S₁ 645 may be operated in two ormore phases. For example, in one phase, switch S₀ 640 may be closed, andswitch S₁ 645 may be open, so that the waveform detector 650 can amplifyand sample a filtered V_(line) waveform “V_(sense)” 655 of voltage inthe hot conductor 620. In another phase, switch S₀ 640 may be open, andswitch S₁ 645 may be closed, so that the capacitance detector 660 canmeasure capacitance C_(sense) 635 of the conductive sense plate 630 toobtain a scaling factor 665 for scaling the filtered V_(line) waveform“V_(sense)” 655.

Accordingly, by controlling the switches S₀ 640 and/or S₁ 645, amultiplexing circuit 600 of a non-contact voltage sensing apparatusaccording to the present disclosure can selectively couple a conductivesense plate 630 to a waveform detector 650 and/or a capacitance detector660. By multiplexing the conductive sense plate 630 between the waveformdetector 650 and the capacitance detector 660, the same conductive senseplate 630 used by the waveform detector 650 can be shared with thecapacitance detector 660 for accurate measurement and signal processing.In addition, the multiplexing allows duplication of components to beminimized.

FIG. 7 is a wiring diagram schematically illustrating electricalcomponents of a waveform detector circuit 700 in accordance with oneembodiment. The waveform detector circuit 700 includes the hot conductor620 with voltage V_(line) 625, earth 610 (reference voltage), conductivesense plate 630 with capacitance C_(sense) 635, and switch S₀ 640 in aclosed position, as described in further detail above with reference toFIG. 6. The illustrated waveform detector circuit 700 is configured toconvert an induced current “i₁” 735 into an amplified voltage signalproportional to the hot conductor 620 voltage V_(line) 625. Thetime-varying AC voltage 625 of the hot conductor 620 induces, throughcapacitive coupling, the induced current i₁ 735, so that the waveformdetector circuit 700 produces a filtered or distorted V_(line) waveformoutput “V_(sense) ^(”) 655.

In the illustrated embodiment, the waveform detector circuit 700 isimplemented as a transimpedance amplifier circuit. Those having ordinaryskill in the art will recognize that alternative implementations, e.g.,other means of current measurement that may include differentcurrent-to-voltage circuitry or other current-sensing circuitry, mayequivalently be used to sense the induced current i₁ 735.

The illustrated waveform detector circuit 700 includes an amplifier 750,e.g., an op-amp. At one input of the amplifier 750, a constant DCreference voltage “V_(re)f” 745 may be used to properly bias thewaveform detector circuit 700. At another input of the amplifier 750,the induced current i₁ 735 is combined with a feedback loop connected tothe output V_(sense) 655. The feedback loop resistance “R_(f)” 755 maybe chosen to provide a gain for the amplifier 750. The amplifier 750 isalso connected to a DC supply voltage V_(CC) 752 and a sensor ground751.

The illustrated waveform detector circuit 700 produces an output signalV_(sense) 655 that scales linearly with the coupling capacitanceC_(sense) 635 and with the voltage V_(line) 625 in the hot conductor620. For example, the illustrated circuit may determine the outputV_(sense) 655 as follows, based on the time-varying voltage V_(line) 625in the hot conductor 620, the coupling capacitance C_(sense) 635 betweenthe conductive sense plate 630 and the hot conductor 620, the inducedcurrent i₁ 735, and the feedback loop resistance R_(f) 755:

${i_{1}(t)} = {C_{sense}\frac{{dv}_{line}(t)}{dt}}$v_(sense)(t) = −i₁(t)R_(F)${v_{sense}(t)} = {{- R_{F}}C_{sense}\frac{{dv}_{line}(t)}{dt}}$${v_{line}(t)} = {{- \frac{1}{R_{F}C_{sense}}}{\int{{v_{sense}(t)}{dt}}}}$

Integrating the determined output V_(sense) 655, the waveform detectorcircuit 700 or signal processing circuitry produces a responseproportional to the time-varying AC line voltage V_(line) 625.

Thus, if the coupling capacitance C_(sense) 635 can be known, the outputV_(sense) 655 of the waveform detector circuit 700 can be used by anon-contact voltage sensing apparatus according to the presentdisclosure to measure the AC line voltage V_(line) 625 in the hotconductor 620.

FIG. 8 is a wiring diagram schematically illustrating electricalcomponents of a capacitance detector circuit 800 (orcapacitance-determining electronic circuitry) in accordance with oneembodiment. The capacitance detector circuit 800 includes the hotconductor 620 with voltage V_(line) 625, earth 610 (reference voltage),and conductive sense plate 630 with capacitance C_(sense) 635, asdescribed in further detail above with reference to FIG. 6. Theillustrated capacitance detector circuit 800 includes node A 825 andnode B 830 to illustrate the formation of capacitance C_(sense) 635 inthe conductive sense plate 630. In the illustrated embodiment, themetallic wire of the energized hot conductor 820 forms node A, and aconductive sense plate (e.g., the conductive sense plate 130 describedabove with reference to FIG. 1 or the conductive sense plate 230described above with reference to FIGS. 2-3) forms node B. Thecapacitance C_(sense) 635 is dependent on physical characteristics ofnode A 825 and node B 830, such as, e.g., a size (e.g., wire gauge) ofthe node A 825 hot conductor 820 and an area and/or shape of the node B830 conductive sense plate. The capacitance C_(sense) 635 is alsodependent on a geometry of a relationship between node A 825 and node B830, such as, e.g., alignment and distance between node A 825 and node B830. Such factors may differ with each installation or application of anon-contact voltage sensing apparatus according to the presentdisclosure. Therefore, a capacitance detector circuit 800 allows moreaccurate determination of the voltage V_(line) 625 in the hot conductor620.

The illustrated capacitance detector circuit 800 includes a relaxationoscillator configured to generate a signal having a frequencyproportional to the capacitance C_(sense) 635 between the hot conductor620 and the conductive sense plate 630. The conductive sense plate 630is discharged by current flow in the following loop: node B 830, sensorground 851, earth 610, neutral, node A 825. The conductive sense plate630 is charged by current flow in the following loop: node B 830, V_(CC)852, sensor ground 851, earth 610, neutral, node A 825. The capacitancedetector circuit 800 produces a voltage output “V_(out)” 860 thatswitches at a switching frequency fv_(out) 865. The switching frequencyfv_(out) 865 of the capacitance detector circuit 800 output V_(out) 860can provide a scaling factor 665 for scaling the filtered V_(line)waveform output V_(sense) 655 from the waveform detector circuit 700.

In the illustrated embodiment, the capacitance detector circuit 800 isimplemented as an astable multivibrator circuit. Those having ordinaryskill in the art will recognize that alternative implementations, e.g.,other means of capacitance measurement that may include differentrelaxation oscillator or capacitance-to-frequency circuitry or othercapacitance-sensing circuitry, may equivalently be used to sense thecapacitance C_(sense) 635. The illustrated relaxation oscillator circuitallows a non-contact voltage sensing apparatus in accordance with thisdisclosure to synthesize a transfer function to easily recover theV_(line) waveform from the filtered V_(sense) 655, at a low powerexpenditure.

The illustrated capacitance detector circuit 800 is astable andcontinuously switches its output V_(out) 860 between V_(CC) 852 and thesensor ground 851 potential (e.g., connected to earth 610 or anotherreference potential). The astable multivibrator circuit includes anop-amp 850, a feedback resistance R_(f) 840, a constant DC referencevoltage V_(ref) 842, and resistances R₁ 841 and R₂ 842. Its outputV_(out) 860 switching frequency fv_(out) 865 depends on a time constantset by feedback resistance R_(f) 840 and the coupling capacitanceC_(sense) 635 formed between the hot conductor 620 and the conductivesense plate 630. For example, the switching frequency fv_(out) 865 ofthe illustrated circuit 800 is inversely proportional to C_(sense) 635.Accordingly, the capacitance detector circuit 800 may determine theswitching frequency fv_(out) 865 as follows:

$\beta = \frac{R_{2}}{R_{1} + R_{2}}$$T_{V_{out}}2R_{F}C_{sense}{\ln\left( \frac{1 + \beta}{1 - \beta} \right)}$$f_{V_{out}} = \frac{1}{T_{V_{out}}}$

Signal processing electronic circuitry may be configured to use theoutput frequency fv_(out) 865 of the coupling capacitance-determiningelectronic circuitry 800 to obtain a determination of the capacitanceC_(sense) 635 and apply that determination to scale the filteredV_(line) waveform output V_(sense) 655 produced by the waveform detectorcircuit 700, which depends on the capacitance C_(sense) 635.

FIG. 9 is a wiring diagram schematically illustrating electricalcomponents of a calibration circuit 900 configured to calibrate acapacitance detector circuit in accordance with one embodiment. In theillustrated embodiment, the calibration circuit 900 includes acapacitance detector 950 that can be calibrated to more accuratelymeasure a capacitance, e.g., the capacitance C_(sense) 635. For example,the capacitance detector 950 may include a portion or all of thecapacitance detector circuit 800 described above with reference to FIG.8 (e.g., a relaxation oscillator).

It also includes two capacitive elements: a fixed, known, or background(e.g., parasitic [possibly unknown and/or changing]) capacitance C_(par)935 between a ground or reference potential and the capacitance detector950, and the possibly variable or unknown coupling capacitance C_(sense)635 formed between the hot conductor 620 and the conductive sense plate630. The calibration circuit 900 also includes a calibration phaseswitch “S₁” 940. The illustrated calibration circuit 900 is configuredto operate in two phases to calibrate the capacitance detector 950.

In Phase A, the calibration phase switch S₁ 940 is open, and thecapacitance detector 950 is only influenced by the capacitance C_(par)935. In Phase A, the capacitance detector 950 is isolated from thecoupling capacitance C_(sense) 635. Accordingly, the output (e.g.,frequency) of the capacitance detector 950 in Phase A is proportional tothe capacitance C_(par) 935.

In Phase B, the calibration phase switch “S₁” 940 is closed, so that thecoupling capacitance C_(sense) 635 is also connected into the circuitincluding the capacitance C_(par) 935 and the capacitance detector 950.Accordingly, the output (e.g., frequency) of the capacitance detector950 in Phase B is proportional to both the capacitance C_(par) 935 andthe coupling capacitance C_(sense) 635. In the illustrated embodiment,the frequency of the capacitance detector 950 in Phase B is proportionalto the sum of capacitance C_(par) 935 and coupling capacitance C_(sense)635.

By comparing the output of the capacitance detector 950 in Phase A withthe output of the capacitance detector 950 in Phase B, the calibrationcircuit 900 (or, e.g., signal processing circuitry and/or controlcircuitry) can obtain a more accurate determination of the couplingcapacitance C_(sense) 635. For example, in the illustrated embodiment,calibration may include taking a difference between two frequencies:C_(sense) α (f_(B)-f_(A)).

The calibration circuit 900 provides a way to dynamically correct forthe effect of any parasitic capacitance C_(par) 935, and/or to calibratea capacitance detector 950. In other implementations, such a correctionmay be performed by a different type of calibration circuit, e.g.,calibration via controlled conditions at manufacturing.

FIGS. 10A-10B are graphs illustrating a sensitivity of sensedcapacitance to conductor size and distance from a conductive senseplate, for a given dielectric constant.

FIG. 10A illustrates a graph 1000 showing a modeled relationship betweendistance and capacitance C_(sense) for wires of different gauges. Thex-axis of graph 1000 displays a distance “d_wire_plate” 1020 between aconductive sense plate and a conductive wire, measured in millimeters(ranging linearly from approximately 1 mm to 20 mm in divisions of 2.5mm) The y-axis of graph 1000 displays a capacitance “C_sense” 1030,measured in Farads (ranging from approximately 10⁻¹⁴ to 10⁻¹¹ Farads, ina logarithmic or other non-linear scale). Capacitance-versus-distancecurves are plotted for four wires of different sizes: 6-gauge (AWG6)wire 1006, 8-gauge (AWG8) wire 1008, 10-gauge (AWG10) wire 1010, and12-gauge (AWG12) wire 1012. For a given wire, capacitance is greater fora smaller distance. For a given distance between the sense plate andwire, capacitance is greater for larger wire.

FIG. 10B illustrates a graph 1050 showing a modeled relationship betweenwire positioning error and percent absolute error of measuring voltageV_(sense) in wires of different gauges. The x-axis of graph 1050displays a distance “d_wire_plate” 1070 between a conductive sense plateand a conductive wire, measured in millimeters (ranging linearly fromapproximately 9 mm to 11 mm in divisions of 0.25 mm) The y-axis of graph1050 displays a “Percent Error Amplitude (V_sense)” 1080, measured inpercentages (ranging linearly from 0 to 20 percent).Error-versus-distance curves are plotted for four wires of differentsizes: 6-gauge (AWG6) wire 1056, 8-gauge (AWG8) wire 1058, 10-gauge(AWG10) wire 1060, and 12-gauge (AWG12) wire 1062. The curves are allcalibrated for a target 10-millimeter distance from the conductive senseplate to the center of the wire, so all of the curves show no errorwhere d_wire_plate is exactly 10 mm. For a given wire, as actualdistance to the sense plate diverges in either direction from thecalibrated distance, the absolute value of the error percentage growslarger. For a given distance between the sense plate and wire,percentage error is greater for larger wire.

FIG. 11 illustrates physical components of an example conductor fixingand measurement system 1100 including a digital caliper in accordancewith one embodiment. A conductor fixing and measurement system 1100 mayimprove measurement of a capacitance C_(sense) and reduce error indetermining an AC voltage V_(sense) (e.g., as illustrated above withreference to FIGS. 10A-10B), for example by enabling a non-contactvoltage sensing apparatus to determine and/or account for a location ofthe conductor to be measured and a size of the conductor to be measured.

In some embodiments, the non-contact voltage sensing apparatus of thepresent disclosure includes conductor measurement means to fix and/ormeasure one or more aspects of a conductor at a measurement region. Forexample, the apparatus may include one or more features configured toguide a conductor to the measurement region (e.g., to a location and/orinto an orientation at the measurement region) and/or to hold theconductor at or in the measurement region. In some embodiments, theapparatus is configured to fix at least a portion of a conductor in oragainst a known position.

The apparatus may include one or more features to obtain a determinationof at least one physical dimension of the conductor. For example, theapparatus may be configured to determine a diameter of a conductor(e.g., a wire including an outer insulating jacket/layer), acircumference of the conductor (e.g., a partial circumference), a wiregauge of the conductor, and/or a cross-sectional area of the conductor.

In the illustrated example, a conductor fixing and measurement system1100 includes a digital caliper. The system 1100 includes an upperhousing 1110 and a lower housing 1115 connected by a hinge 1116. Theupper housing 1110 and lower housing 1115 close around a measurementregion 1120 configured to receive a conductor 1122. The conductor 1122is pressed between a fixed caliper jaw 1130 within the lower housing1115 and a movable caliper jaw 1140 (e.g., slidable) within the upperhousing 1110. The movable caliper jaw 1140 is connected to a pair ofguide rails 1145 that can move within rail receivers 1140 in the upperhousing 1110, allowing the movable caliper jaw 1140 to adjust toaccommodate different sizes of conductor 1122. A tension leaf spring1160 or other resilient element provides spring force to move or pressthe movable caliper jaw 1140 against the conductor 1122.

In operation, the conductor fixing and measurement system 1100 includesa sliding measure 1170 (e.g., attached to or part of a guide rail 1145)that indicates, by the location of the movable caliper jaw 1140, thesize (e.g., diameter) of the conductor 1122. For example, the slidingmeasure 1170 may include conductive, capacitive, resistive, magnetic,and/or optical elements readable by an electrical contact, magnetichead, or optical reader 1180. For example, the sliding measure 1170 mayinclude a PCB with metallic fingers at a periodic spacing, and thereader 1180 may include a conductive sense electrode and/or capacitancedetector circuit (e.g., on another PCB). When the measure 1170 PCB moveswith respect to the reader 1180, the capacitance changes periodically asthe conductive fingers (e.g., triangles) of the sliding measure 1170slide past the reader 1180. A microcontroller can count the periodicchanges in capacitance corresponding to the changing positioning of thesliding measure 1170 attached to the movable caliper jaw 1140. Thus,based on the known finger spacing and the count of capacitance changes,the microcontroller may determine an absolute positioning of the movablecaliper jaw 1140 with respect to the reader 1180. This allows precisemeasurement of the diameter of the conductor 1122. In some embodiments,the conductor fixing and measurement system 1100 includes an absolutepositioning identification system (e.g., a binary code reader) thatincorporates mechanical, electro-magnetic, and/or optical positioncoding.

From the total diameter of the conductor 1122 (including approximatelytwice the thickness of its insulating jacket), the microcontroller cancalculate a probable wire gauge and probable insulation thickness. Forexample, known insulation and/or wire gauge standards may enable theconductor fixing and measurement system 1100 to categorize the conductorinto one of a set of discrete categories, e.g., if a thickest 6-gaugewire is smaller than a thinnest 4-gauge wire. Based on thosecalculations, the conductor fixing and measurement system 1100 canestimate a distance between the center of the wire and the conductivesense plate.

A non-contact voltage sensing apparatus may include a conductor fixingand measurement system 1100 or a functional equivalent to improve theaccuracy of determining a coupling capacitance between a targetconductor and a conductive sense plate, so that the apparatus provides amore accurate determination of an AC voltage in the target conductor.

FIG. 12 is a wiring diagram 1200 schematically illustrating multiphasecoupling capacitances. Conventionally, shielding (such as shield 125described above with reference to FIG. 1) has not been considerednecessary in measuring an AC circuit. The inventors have discovered,however, that shielding can be surprisingly important for non-contactvoltage sensing in multiphase (e.g., three-phase) environments.

For example, without shielding, a current can undesirably be injectedinto a waveform detector 650 from an energized non-target AC voltagephase. The wiring diagram 1200 schematically illustrates an examplemultiphase environment in which the waveform detector 650 is intended tomeasure the voltage on a first conductor VA 1220 with respect to aground 1210 potential. The multiphase environment includes additionalconductors VB 1230 and V_(C) 1240 energized with AC voltages ofdifferent phases. As a result, the waveform measured by waveformdetector 650 may be corrupted by capacitances 1235, 1245 between thewaveform detector 650 and conductors VB 1230 and V_(C) 1240, andpotentially capacitances 1237, 1247 between the sensor ground 1215potential and conductors VB 1230 and V_(C) 1240. As a result of thecurrents injected from these non-target phases, the output V_(sense) 655may be incorrect. Therefore, the disclosed non-contact voltage sensingapparatus is shielded to reduce the influence of undesired capacitancesas described above.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat alternate and/or equivalent implementations may be substituted forthe specific embodiments shown and described without departing from thescope of the present disclosure. For example, although variousembodiments are described above in terms of a housing that snaps arounda conductor, in other embodiments various other form factors may beused. In addition, processing and/or output readings may be providedlocally at the apparatus and/or performed or displayed remotely. Thespirit and scope of this application is intended to cover anyadaptations or variations of the embodiments discussed herein.

Thus, although the subject matter has been described in languagespecific to structural features and/or methodological acts, it is alsoto be understood that the subject matter defined in the appended claimsis not necessarily limited to the specific features or acts described.Rather, the specific features and acts are disclosed as example forms ofimplementing the claims. This application is intended to cover anyadaptations or variations of the embodiments discussed herein.

1-22. (canceled)
 23. A non-contact voltage sensing apparatus asdescribed and illustrated herein, comprising a capacitive sensingmechanism capable of measuring a voltage between a hot conductor of analternating current (AC) electrical circuit and a reference potential,without direct electrical contact to the hot conductor and withoutreference to any other AC voltage signal.